Method and apparatus for electrostatically separating particles having different electrical properties



July 13, 1948. 11.1. MASSE 2,445,229 x METHOD AND APPARATUS FORELECTROSTATICALLY SEPARATING PARTICLES HAVING DIFFERENT ELECTRICALPROPERTIES Filed April 5, 1944 TnpMAs JERaMMA ss A-r-rpRK Patented July13, 1948 METHOD AND APPARATUS FOR ELECTRO- STA'IIOALLY SEPARATINGPARTICLES HAVING DIFFERENT ELECTRICAL PROP- ERTIES Thomas Jerome Masse,Alexandria, near Sydney,

= New South Wales, Australia Application April 5, 1944, Serial No.529,584

In Australia April 14, 1943 15 Claims.

This invention relates to improvements in method of and apparatus forseparating for collection components of mixtures of materials which havediilerent electrical properties. Such materials may be a mixture of twoor more powdered, granular, shredded or such like solid materials. Theinvention is, for example, applicable to the removal from mixtures ofmaterials of particles, say rubber, glass or ebonite or the likeelectrical insulation material from the particles of some otherelectrical insulation material, or the particles of a metal or otherelectrical conductive material.

The invention has relevance more particularly to a modification of themethod of and means which are the subject-matter of my Patent No.2,317,210 of the United States of America, dated April 20, 1943, for aninvention entitled "Method and apparatus for separating textile materialfrom rubber."

According to the method of operation for treatment of materials thesubject of the aforesaid Letters Patent, fabric fragments are separatedfrom rubber fragments by steps which include passing a mixture of saidfragments into an electrostatic field between a repelling electrode anda collector electrode, the said electrodes being electrically charged toan extent whereby the fabric fragments move from the mixture and adhereto said collector electrode and by which they are removed andtransferred for collection.

The apparatus according to the subject of the aforesaid Letters Patentconsists of an inclined screen to which the mixture to be operated on isfed, a flat repelling electrode aligned with said screen, means forvibrating said screen and said repelling electrode, at least onerotatable collector electrode having a 'metal core, a wrapping ofdielectric material for said core, and an encasement for said wrappedcore of a material having a minutely tentacled surface, means forestablishing a high tension electrostatic field between said electrodes,and suction means for removing fragments adhering to the collectorelectrode. In some cases a counter-charging electrode may be providedtogether with means for establishing a high tension electrostatic fieldof one polarity between said collector electrode and said repellingelectrode and for establishing a high tension electrostatic field ofopposite polarity between said counter-charging electrode and saidrepelling electrode. Further, said apparatus might also include aheating element and a reflector for providing a localised airconditioning unit to 2 enable the collector encasement to be kept in drycondition.

According to the method of the present invention the mixture ofmaterials to be treated for the recovery of different particles thereofis moved through an electrostatic field established between a repellingelectrode and an attracting electrode, said electrodes are held in suchspaced relationship to each other and are so electrically charged thatthe field strength between them will influence certain particles of thesaid moving mixture to a rising position with respect to said repellingelectrode, as a mass which may contact the attracting electrode withoutlosing con act with said moving mixture; and the said mass is translatedby its continuing contact with said moving mixture to a zone ofseparation .where the said particles are subjected to a suction elementfor collection away from said moving mixture. Preferably, the mixture ispassed by gravity over an inclined table constituting the repellingelectrode, while being vibrated to facilitate the movement andseparation; and before this it is disintegrated or shredded so as toproduce at least one of its components in particles of elongated orshredded form.

Apparatus usable for carrying out the above method is of simplecharacter. The construction and arrangement of the repelling electrodewith the attracting electrode and the construction of the latter arehereinafter referred to. The said apparatus is mainly differentiated inits working and construction and arrangement from the apparatus usablein connection with the method of my invention the subject-matter of myprior patent aforesaid, by the facts that apparatus according to thepresent invention is operable without the separated particles of themixture having to adhere to the attracting electrode to be carried outof the electrostatic field; that the attracting electrode is stationaryand does not rotate as is the case with the collector electrode referredto in connection with my patent before-mentioned; and that the mixtureof materials when moving through the electrostatic field, carries theseparated particles to a suction element from whence they aretransferred for collection. The improvements herein disclosed not onlyhave the advantage of relative simplicity, but they also serve moreefficiently for separating the components of certain mixtures, such as,for example, the fabric from;the rubber of de-trea'ded pneumatic tires.

For a better understanding of the invention, reference is now made tothe accompanying drawings in which are diagrammatically shown preferredforms of apparatus suitable for use in practicing the invention.

In these drawings: I

Fig. 1 is a sectional 'view' of one form of the apparatus, theattracting electrode being shown in curved formation.

Fig. 2 is an enlarged view of part of Fig. 1 showing the two electrodes.

Fig. 3 is a sectional view of a modified form of the attractingelectrode.

Fig. 4 is another sectional view of a further modified form of theattracting electrode, and

Fig. 5 is a broken side elevational view partly in section of the twosaid electrodes and part of the framing associated with one of the saidelectrodes.

In the drawings (Fi 1) the mixture of materials to be treated for therecovery of different particles therefrom,is fed on to a vibratory table6 from a hopper I. The hopper may be associated with a disintegratormill (not shown). The table is supported on flexible legs IA and avibratory unit 8, rotated by a motor 9, imparts to the table a vibratoryefl'ect. The mixture of materials passes along spreader boards In and onto an inclined screen ll through which very fine granules of thematerial will pass. These fine granules which are indicated by plainarrows, will then pass through chute l2 for collection.

Shreds. of the mixture of materials (indicated by single barbed arrows)and large granules (indicated by double barbed arrows) of the mixture ofmaterials are caused to travel over the screen ll towards the lower endthereof and pass into the electrostaticfleld 13 formed -by anelectrically charged stationary attracting electrode H and a repellingelectrode I5. The attracting electrode is. associated with a suctionelement l6, directly in contact with the electrostatic field. Theattracting electrode I4 is shown in Fig. 1 and Fig. 2 with a curvedplate of dielectric material, say wood, Bakelite or the like, whichcarries thereon. an electric conductive wire II which may be arranged insinuous form. This electrode may be charged through a. rectifier valveMa. The outer surface l8 of the attracting electrode is smooth.

Shreds of material and large granules of material indicated at I! (Fig.2) are passed into the electrostatic held, and the material to becollected. which in this case consists of the shreds of materialindicated at 20. are attracted to the attracting electrode, whilstmoving through the electrostatic field, in the following manner. Some ofthe shreds are attracted to the attracting electrode with a hair-on-endeffect, other shreds are attracted to the already attracted shreds, incontact with the attracting electrode, while a further series of shredsare attracted to the second mentioned attracted shreds and so on. Theattracted shreds stand in a more or less upright pyramidical directionin mass formation and the mass or masses of the attracted shreds, at thebottom end thereof, being associated with the downwardly movingunattracted mixture are caused to be carried towards the suction elementI6, from whence the attracted shreds are transferred for collection.Uncollected particles of the mixture pass through the electrostaticfield into a chute 2| where they may be passed back to the disintegratorby the action of fan 22 for further treatment- Fig. 2 shows the mixtureof materials l9 passing downwardly over the screen II and over the 4repelling electrode IS. The attracted shreds are shown in mass formationat 23.

Although I have described by way of example a manner in which the shredsare attracted under the influence of the electrostatic field, it is tobe understood that any number of a series of shreds may be attracted toeach other. In any case the mass of attracted shreds at their bottom endis always contacting the downwardly moving mixture of materials so thatthe shrutls in their upraised position are carried to the suctionelement.

The outer surface We of the attracting electrode l4 being smooth; theattracted shreds, although some of them are in electrical contact withthe smooth surface, do not adhere to the attracting electrode as is thecase in my patent ai'oresaid. In my patent aforesaid, the attractingelectrode is coated with felt or other material having a minutelytentacled surface and is rotated, so that the attracted shreds adherethereto and are carried thereby out of the electrostatic field forcollection. I

Although the drawing (Fig. 1) shows only one pair of electrodes, it isto be understood that more than one pair of electrodes may be used on asingle vibratory table.

Instead of the attracting electrode being constructed as shown in Fig. 1and Fig. 2 of the drawings, it may consist 01' a flat dielectric plate24 as shown in Fig. 3 and Fig. 4. In the construction shown in Fig. 3,the flat dielectric plate 2| is shown with conductive wire 25 thereon,which may be arranged in sinuous formation. In the construction shown inFig. 4 the flat dielectric plate 24 is shown with a conductive flatmetal plate 26 thereon. The curved dielectric plate' shown in Fig. 1 andFig. 2 may also incorporate a curved conductive plate instead of theconductive wire as shown.

In every case the attracting electrode is stationary and the plate ofthe attracting electrode is of dielectric material such as wood, eboniteor the like. The outer surface of the plate is smooth so that theparticles of the mixture undergoing treatment which contact the plate,will slip along the plate surface.

The repelling elecrode l5 may consist of a metal plate and is earthed at21. As an alternative the repelling electrode may consist of an extendedportion of the screen II.

The suction unit is associated with the attracting electrode. This unitcomprises one or more slotted members 28, which are open at one end toreceive particles which have been treated; the other ends open into aconduit or conduits 29 in communication with a fan 30 and conduits 31whereby treated particles are transferred directly from theelectrostatic field between the electrodes.

The attractin electrode may be insulated from the conduits in anysuitable manner.

The distance between the adjacent surfaces of the electrodes [4 and I5may be adjustable by providing for adjustment of the electrode It inrelation to the electrode [5, so that the dielectric capacity will notbe interfered with, and so that the attracted particles which are inmass formation, can move relatively to the downwardly moving unattractedmixture of materials. through the electrostatic field and into contactwith the suction element. I

Instead of the electrodes I4 and I5 being associated with a vibratoryscreen as shown in Fig. i of the drawings, the repelling electrode 15may comprise an electrically earthed endless driving belt arrangementwith or without any vibratory effect.

The electrical current may be supplied to the electrodes in similarmanner to that disclosed in my beforementioned Letters Patent:

It will be understood that various modifications of and departures fromthe details of the foregoing description and drawings may be madewithout departing from the improvements of my invention, which areintended to be defined in the claims.

What isciaimed is:

l. The method of separating components of a mixture of,disintegratedmaterials having different electrical properties, whichcomprises passing a stream of such mixture over a support into a hightension electrostatic field between a repelling electrode constitutingpart of said support and an attracting electrode spaced thereabovehaving a face of dielectric material, hold? ing said electrodes sospaced from each other and so charged that selective particles arelifted from said mixture by said field as the stream enters said fieldto form a mass of such particles contacting said dielectric material andyet maintaining contact with said stream, continuing the movement ofsaid stream through said field so that said stream drags said mass oflifted particles along said face into a zone of separation across itspath, and suctionally drawing and conducting such lifted articles awayfrom said stream in said zone.

2. A method as described in claim 1 wherein the mixture is disintegratedso as to form shreds of at least one of its components before it ispassed into said field.

. 3. A method as described in claim 1 wherein the mixture is passed oversaid support into and through said field by vibrating said support whileholding it inclined downward towardsaid repolling electrode andcontinuously feeding said mixture onto an upper part of said support.

4. The method of separating fabric fragments from a mixture ofdisintegrated rubber and fabric which comprises moving the mixture on asupporting member into a high tension electrostatic field maintainedbetween'a repelling electrode constituting part of said member and asuperposed attracting electrode having a face of dielectric material, somaintaining the depth and strength of said field that fabric fragmentsare lifted from said mixture to form a mass of co herent fabricparticles in contact with said face and with the residue of said mixtureat the upper and lower extremities, respetcively, of said mass,continuing the movement of said residue on said member through saidfield and thereby dragging said mass of fabric fragments along said faceto a zone of separation across the path of said mass, and suctionallyremoving fabric fragments from said mass in said zone.

5. A method as described in claim 4 wherein the said member is inclinedand vibrated so that the mixture is moved continuously by gravity intoand through said field.

6. A method as described in claim 4 wherein said mixture is firstdisintegrated into particles largely of shred-like form, then isscreened to separate fine granules therefrom, and thereafter is treatedas aforesaid.

7. In an apparatus for separating electrostaticaily components of amixture of materials having different electrical properties, astationary attracting electrode of extended surface area having a faceof dielectric material, a repelling electrode therebelow, means forcharging said attracting electrode to establish an electrostatic fieldbetween said electrodes, means to move such mixture on said repellingelectrode into and through said field,'said electrodes being so spacedapart and so charged that selective particles of the mixture enteringsaid field are lifted to form a suspended mass of such particlescontacting said face and yet maintaining contact with the residue ofsaid mixture, whereby said mass is dragged along said-face as saidmixture continues to be moved into and through said field, and suctionmeans opening at said face across the path of movement of said mass tocreate a zone of suction for drawing and conducting such liftedparticles away from said mixture.

8. An attracting electrode for apparatus of the character described,comprising a plate of dielectric material having a smooth face, anelectrically conductive element disposed over and on the back of saidplate, and a tubular element constituting a part of suction meansarranged "to open at the face of said plate and to extend backwardlytherefrom.

9. An attracting electrode for apparatus of the character described,comprising a curved plate of dielectric material having a smooth face,an electrically conductive wire extending over and on the back of saidplate, and a tubular element constituting a part of suction meansarranged to open at the face ofsaid'plate and to extend backwardlytherefrom.

' electric material having a smooth face, an electrically conductiveelement extending over and on the back of said plate, and a tubularelement constituting a part of suction means extending backwardly fromsaid plate and opening at said face near the central portion thereof 12.In an apparatus for separating electrostatically components of a mixtureof disintegrated materials having different electrical properties, atable having an inclined surface formed at least in part by a groundedelectrically conductive member constituting a repelling electrode, meansto feed the mixture onto an upper part of said table, means forvibratineasaid table to agitate and move said mixture continuously downsaid surface, an attracting electrode mounted above said member, saidattracting electrode comprising a stationary plate of dielectricmaterial having a smooth face and an electrically conductive backingelement, means for charging said attracting electrode to establish anelectrostatic 13. Apparatus as described in claim 12, and a collectorfor the residue of said mixture at the lower end of said table.

14. Apparatus as described in claim 12 wherein said member forms a lowerpart of said table and an upper part thereof comprises a screen.

to sift fine granules out of said mixture before the mixture moves intosaid field.

15. In an apparatus for separating electrostatically components of amixture of mateirals having diflerent electrical properties, astationary attracting electrode of extended surface area having a faceof dielectric material, a repelling electrode therebelow, means forcharging said attracting electrode to establish an electrostatic fieldbetween said electrodes, means to move such mixture on said repellingelectrode into and through said field, said electrodes being so spacedapart and so charged that selective particles of the mixture enteringsaid field are lifted to form a suspended mass of such particlescontacting said face and yet maintaining contact with the residue ofsaid mixture, whereby said mass is dragged along said face as saidmixture continues to be moved into and through said held, and suctionmeans opening at said face across the path of movement of said mass tocreate a zone of ductive element disposed over and on the back of.saidplate, and a tubular element constituting a part of said suctionmeans arranged toopen at the face of said plate and to extend backwardlytherefrom.

THOMAS JEROME REFERENCES CITED The following references are of record inthe file. of this patent:

' UNITED STATES PATENTS Number Name Date 4 670,440 Sutton Mar: 26, 1901'1,179,936 Kraus Apr. 18, 1916, 1,355,477 Howell Oct. 12, 1920 1,549,875Home Aug. 18, 1925 2,306,105 Grave Dec. 22, 1942 FOREIGN PATENTS NumberCountry Date suction for drawing and conducting such lifted particlesaway from said mixture, sa-id attracting electrode comprising a plate ofdielectric material having a smooth face, an electrically con-..

Australia Sept. 25, 1940

